1. Field of the Invention
This device relates generally to electric indicator and control devices and more particularly to indicator and control devices that can be retro-fitted or added onto a circuit board.
2. Description of the Prior Art
Complex electronic apparatus typically have their circuitry constructed in small subcircuit modules so that, should the apparatus break down, it is easier to fix. A preferred method for modulizing an electronic circuit is to form each subcircuit on a plug-in "card" which has printed circuit traces formed along one edge which touch contacts within a card-receiving connector attached to a mother board of the electronic apparatus.
These cards allow a repair technician to unplug a defective subcircuit card from the mother board and substitute a working subcircuit card for it, if he can figure out which card is defective. The problem is that in most electronic apparatus, cards are arranged in closely packed, space-saving rows. Unfortunately for the repairing technician, these closely packed cards are virtually impossible to test while still plugged into the mother board. In consequence, a technician must remove a card from the electronic apparatus in order to test it, which presents yet another problem; namely, that it is much more difficult to test a removed subcircuit card than it is to test it in situ.
Frank Draper Babcock partially addressed this problem in U.S. Pat. No. 3,573,558 in which he disclosed a printed circuit handle having a slot with a number of contacts positioned therein for making electrical connections with traces formed on an edge of a printed circuit card. Lights and switches were disposed within recesses formed on the front of the handle and were electrically connected to the contacts of the slot. The lights of Babcock's invention could be used to display potentials at several locations in the subcircuit and the switches could be wired to interact with the card's subcircuit in various ways. A circuit board outfitted with Babcock's handle can be tested to a limited degree and even functionally modified without being removed from the mother board of the electronic apparatus.
Drawbacks of Babcock's invention include that it is a special purpose device which can only be used with a printed circuit board specifically designed for his handle and that it is an expensive device due to its relative mechanical complexity. Also, the switches and indicators of Babcock's invention are nonstandard and must be manufactured solely for their use in his PC board handle device.